Temperature control using time proportional output of a heater

ABSTRACT

A temperature control unit according to one or more embodiments may include an acquisition unit that is configured to acquire an operation amount from a controller, and an SSR control unit that is configured to perform time proportional output of an instruction to drive or stop a heater to SSR after reflecting the operation amount.

TECHNICAL FIELD

The present invention relates to an output control unit that performsoutput control of an output apparatus according to information from acontrol apparatus.

RELATED ART

Conventionally, in the field of factory automation (FA), a systemconfiguration is adopted in which a controller such as a PLC(programmable logic controller) controls various input/output units suchthat the input/output units exchange data with input/output apparatuses.FIG. 7 is a diagram showing an outline of a conventional output controlsystem. FIG. 7 shows a system in which a heater is used to control thetemperature of a target object, as an example. As illustrated, acontroller transmits various instructions or various types ofinformation to various units, and the various units collect data from aninput/output apparatus (e.g., a temperature sensor).

RELATED ART DOCUMENTS Patent Documents

Patent Document 1: Japanese Publication of Unexamined Patent Application“JP-A-2007-280142” (Publication date: Oct. 25, 2007)

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

Incidentally, in a system that performs temperature control as shown inFIG. 7, a heater, which is an example of an output apparatus isconnected to a digital output unit via an SSR. In addition, the digitaloutput unit, which is an example of various units is connected to acontroller via a network. In such a system, temperature control isperformed by the digital output unit turning on and off the heater viathe SSR in accordance with time proportional output (TPO) from thecontroller. Here, “time proportional output” refers to an output methodfor proportionally changing an ON/OFF time ratio as output.

A conventional controller as shown in FIG. 7 sets a value indicating anON/OFF time ratio of an output apparatus as a setting value, and causesthe apparatus to which the controller belongs to calculate on and offtimes of the output apparatus that are derived from the setting valueand a predetermined control cycle of the above-described TPO. Morespecifically, a configuration has been adopted in which a user programfor calculating on and off times of the output apparatus based on thevalue indicating an ON/OFF time ratio of the output apparatus and thevalue of the control cycle of the above-described TPO is stored in thecontroller in advance, and the controller executes the user program.Note that the user program is created according to a control purpose ofthe user. The controller has then output, to various units, eitherinformation including an instruction to turn on the output apparatus orinformation including an instruction to turn off the output apparatus,according to the calculated times.

However, if such a communication system is adopted for apparatuses,there has been a risk that there are deviations of TPO depending on thecycle time of a controller and a TPO control cycle. In the followingdescription, for simplification, the control cycle of the controller andthe communication cycle of the network are synchronized. FIGS. 8A to 8Care diagrams showing the relationship between a setting value that isset by a controller and the value of an instruction to turn on or off anoutput apparatus (output value) that is actually output by thecontroller to various units, in a conventional output control system.FIG. 8A is a diagram showing an ideal relationship between a settingvalue and an output value. It is ideal that an ON/OFF time ratioindicated by the output value matches the setting value as illustrated.In addition, if the apparatus to which the controller belongs changesthe setting value, it is desirable that the controller adjusts theoutput value to the various units as well such that the changed settingvalue can be realized. For example, if the setting value is changed from50% to 5% as illustrated, it is ideal that the controller sets theoutput value to ON for the period of 5% of one TPO control cycle invarious units, and sets the output value to OFF for the 95% remainingtime.

However, if setting value is set without taking the relationship betweenthe cycle time of the controller itself and the TPO control cycle of thevarious units into consideration, there is a risk that ideal outputcontrol as shown in FIG. 8A cannot be realized. For example, if thesetting value is set such that a time during which the output apparatusis driven in one TPO control cycle is shorter than the cycle time of thecontroller, the setting value and the output value do not match. Forexample, if the setting value is 5%, and the TPO control cycle is 2seconds(s), then the controller should set the output value to ON for0.1 s, and set the output value to OFF for 1.9 s.

However, if the cycle time of the controller is 0.5 s as shown in FIG.8B, then the minimum time unit by which the controller can change theoutput value is 0.5 s. Therefore, for example, even if the setting valueis set to 5%, it is not possible to realize control in which the outputvalue is ON for the period of 0.1 s as described above. As a result, asshown in FIG. 8B, the output value is on for the period of 0.5 s, and isOFF for the remaining period of 1.5 s.

In addition, also if a time during which the output apparatus is to bedriven in one TPO control cycle is indivisible by the cycle time of thecontroller, the setting value and the output value do not match. Forexample, as shown in FIG. 8C, if the TPO control cycle is 2 s, the cycletime of the controller is 0.6 s, and the setting value is 50%, thecontroller can switch the output value only in units of 0.6 s.Therefore, as illustrated, the ON/OFF ratio of output determined by thesetting value cannot be realized.

The invention has been made in light of the above-described problem, andaims to reduce TPO deviation due to a cycle time of a controller.

Means for Solving the Problems

In order to solve the above-described issue, an output control unitaccording to the invention includes an acquisition unit that acquires,from a control apparatus, an operation amount for a switching apparatusthat switches between driving and stopping of an output apparatus, andan instruction output unit that performs time proportional output to theswitching apparatus based on the operation amount acquired by theacquisition unit.

Also, in order to solve the above-described issue, a control method ofan output control unit according to the invention includes anacquisition step of acquiring, from a control apparatus, an operationamount for a switching apparatus that switches between driving andstopping of an output apparatus and an instruction output step ofperforming time proportional output to the switching apparatus based onthe operation amount acquired in the acquisition step.

Effects of the Invention

The invention has an effect of eliminating deviation of TPO due to acycle time of a controller.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the main configuration of apparatusesand units included in an output control system according to a firstembodiment of the invention.

FIG. 2 is a diagram showing an outline of the above-described outputcontrol system.

FIG. 3A is a timing chart showing temporal change of input/outputparameters in a temperature control unit included in the above-describedoutput control system.

FIG. 3B is a timing chart showing a portion of FIG. 3A in more detail.

FIG. 4 is a flowchart showing a flow of warning output processing thatis performed by the above-described temperature control unit.

FIG. 5 is a timing chart showing change in an operation amount andchange in instruction output of a temperature control unit according toa second embodiment.

FIG. 6 is a timing chart showing changes in an operation amount and animmediate output instruction that are output from a controller accordingto a third embodiment, and time proportional output (TPO) in atemperature control unit according to the third embodiment and a controlcycle thereof.

FIG. 7 is a diagram showing an outline of a conventional output controlsystem.

FIGS. 8A to 8C are diagrams showing the relationship between a settingvalue and an output value, in a conventional output control system.

EMBODIMENTS OF THE INVENTION First Embodiment

A first embodiment of the invention will be described below withreference to FIGS. 1 to 4. To begin with, an output control system 100according to this embodiment will be described with reference to FIGS. 1and 2.

Apparatuses Included in System and their Connection

The output control system 100 is a system for adjusting the temperatureof a certain target object (e.g., a resin or water), and is a system fordetecting whether or not a heater, a cooling apparatus, or the like thatis used for temperature adjustment is properly driven or stopped. Tobegin with, apparatuses (units) included in the output control system100 and their connection will be described with reference to FIG. 2.FIG. 2 is a diagram showing an outline of the output control system 100.The output control system 100 includes at least a controller (controlapparatus) 2, a temperature control unit (output control unit) 3, aheater (output apparatus) 7, an SSR (solid state relay, switchingapparatus) 8, and a CT (current transformer, measurement apparatus) 9.The output control system 100 may also include a programmable displaydevice 1, a temperature input unit 4, and a temperature sensor 5, whichare not necessary constituent elements.

As illustrated, the controller 2 is connected to the programmabledisplay device 1, the temperature control unit 3, and the temperatureinput unit 4 via a communication coupler using a field network. Also,the temperature control unit 3 is connected to the controller 2, the SSR8, and the CT 9. In addition, the temperature input unit 4 is connectedto the controller 2 and the temperature sensor 5. Furthermore, the SSR8, the CT 9, and the heater 7 are connected to each other along with aheater power supply using an electric wire.

Main Configuration of Each Apparatus

Next, actions of the apparatuses (units) will be described withreference to FIG. 1. FIG. 1 is a block diagram showing a mainconfiguration of the apparatuses and units included in the outputcontrol system 100.

Programmable Display Device 1

The programmable display device 1 is an HMI (human machine interface)that outputs, from the terminal thereof, data and notifications receivedfrom the controller 2 (displays data and notifications on a displayunit, or outputs sound such as an alarm), and thereby presents the dataand notifications to the user. Note that a configuration may also beadopted in which the programmable display device 1 has an input unit,and the input unit transmits an instruction received from the user tothe controller 2.

Controller 2

The controller 2 is a PLC (programmable logic controller) that receivesdata blocks circulating around a communication network that is a fieldnetwork (hereinafter, simply referred to as “communication network”),adds various types of data in the data blocks, and returns the datablocks including the various types of data to the above-notedcommunication network. Here, “data block” refers to a collection of datathat circulates (is exchanged periodically) between various devicesconnected to the communication network. The cycle of circulation of thedata blocks is determined according to the cycle time of the controller2.

The temperature control unit 3 connected to the communication networkreceives the data blocks, and reads various types of data, which will bedescribed later in detail. In addition, the controller 2 reads varioustypes of data included in the data blocks by the temperature controlunit 3 and the temperature input unit 4. More specifically, thecontroller 2 includes a first communication unit 21, a storage unit 22,a second communication unit 23, and a control unit 20.

The first communication unit 21 performs communication between thecontroller 2 and the programmable display device 1. Upon receivingvarious types of data and warnings from the control unit 20, the firstcommunication unit 21 transmits the data and warnings to theprogrammable display device 1. In addition, upon receiving a userinstruction from the programmable display device 1, the firstcommunication unit 21 transmits the user instruction to the control unit20.

The storage unit 22 stores user programs. Here, “user program” is aprogram that specifies various operations and settings of the controller2. A user program is generated by a setting tool (application) and thelike installed in a general-purpose computer or the like, is downloadedto the controller 2 connected to the general-purpose computer, and isstored in the storage unit 22. For example, a user program may include aprogram that specifies the times when the heater 7 should be driven orstopped. A user program is read out and executed by the control unit 20.

The second communication unit 23 performs communication between thecontroller 2, the temperature control unit 3, and the temperature inputunit 4. The second communication unit 23 adds, in a data block,information indicating a control instruction generated by the controlunit 20, or information indicating the values of various parametersrelated to control and the like, and returns the data block to thecommunication network. The temperature control unit 3 connected to thecommunication network acquires the information by receiving the datablock.

In addition, if the data block includes a warning from the temperaturecontrol unit 3 that the heater 7 is disconnected (hereinafter, simplyreferred to as “warning”), the second communication unit 23 transmitsthe warning to the control unit 20. Also, if the data block includestemperature data (information indicating the temperature of an objectthat is subject to temperature adjustment) from the temperature inputunit 4, the second communication unit 23 transmits the temperature datato the control unit 20.

The control unit 20 performs the overall control of the controller 2.The control unit 20 generates information regarding temperatureadjustment (e.g., a control instruction or various parameters) byexecuting a user program read out from the storage unit 22, or using amethod determined in advance for the apparatus in which the control unit20 is included. Here, the “information regarding temperature adjustment”is information that is output by the controller 2, and is informationthat specifies driving and stopping of the heater 7. The control unit 20outputs generated information via the second communication unit 23. Notethat the control unit 20 may also adjust the content of the aboveinformation, for example, degrees of driving and stopping of the heater7 based on temperature data acquired by reading the data included in adata block.

Temperature Control Unit 3

The temperature control unit 3 is a unit that gives an instruction tothe SSR 8 according to information from the controller 2, through timeproportional output (TPO). The temperature control unit 3 is also a unitthat determines, based on the content of an instruction transmitted tothe SSR 8 and a current value acquired from the CT 9, whether or not theheater 7 is disconnected, and if it is determined that the heater 7 isdisconnected, transmits a warning to the controller 2. Morespecifically, the temperature control unit 3 includes an acquisitionunit 30, an SSR control unit (instruction output unit) 32, a currentvalue acquisition unit (measured value acquisition unit) 33, adetermination unit 34, and a warning output unit 35.

The acquisition unit 30 acquires information from the controller 2, andtransmits the information to the SSR control unit 32. The acquisitionunit 30 may also acquire a warning event cancellation instruction (aninstruction to cancel a warning to be described later) from thecontroller 2. If a warning event cancellation instruction is acquired,the acquisition unit 30 transmits the cancellation instruction to thewarning output unit 35.

The SSR control unit 32 transmits an instruction to drive or stop theheater 7 to the SSR 8 in accordance with information acquired from theacquisition unit 30. Here, an instruction to drive the heater 7 and aninstruction to stop the heater 7 are output using TPO. The current valueacquisition unit 33 acquires, from the CT 9, the value of a current(current value) that is flowing in the heater 7 at the timing when theSSR control unit 32 transmits an instruction to the SSR 8, and transmitsthe current value to the determination unit 34.

The determination unit 34 determines, based on the content of aninstruction (a driving instruction or a stop instruction) transmitted tothe SSR 8 and the current value, whether or not the heater 7 is beingdriven and stopped according to the instruction, or whether or not theheater 7 is disconnected. More specifically, if the instructiontransmitted to the SSR 8 is an instruction to drive the heater 7, andthe current value acquired from the current value acquisition unit 33 issmaller than or equal to a predetermined disconnection determinationthreshold (a first threshold), the determination unit 34 determines thatthe heater 7 is disconnected. Note that the disconnection determinationthreshold is a value that is lower than a lower limit value of a currentvalue when the heater 7 is being driven, and may be determined asappropriate. If it is determined that the heater 7 is disconnected, thedetermination unit 34 transmits the determination result to the warningoutput unit 35.

Upon receiving, from the determination unit 34, the result of thedetermination that the heater 7 is disconnected, the warning output unit35 generates a warning, and outputs the warning to the controller 2. Thewarning that is output by the warning output unit 35 may be informationto be handled as one kind of monitoring information by the controller 2(monitoring information warning). The warning that is output by thewarning output unit 35 may also be a warning (minor fault) thatcontinues until some warning cancellation instruction is received fromthe controller 2.

SSR 8, CT 9, and Heater 7

The SSR 8 is a circuit for controlling start and stop (ON and OFF) ofthe heater 7. The SSR 8 drives or stops the heater 7 according to adriving instruction or a stop instruction received from the SSR controlunit 32 of the temperature control unit 3. The CT 9 measures the valueof a current that flows in the heater 7. In other words, it can be saidthat the CT 9 measures an actual operation of the heater 7. The CT 9 maydirectly measure the current that flows in the heater 7, or mayindirectly measure the current that flows in the heater 7. The CT 9transmits the measurement result to the current value acquisition unit33 of the temperature control unit 3. The heater 7 warms an object suchas a resin or water that is subject to temperature control. Theconfiguration of the heater 7 is not limited as long as the heater 7 iselectrically driven and can transfer heat to a target object.

Temperature Sensor 5 and Temperature Input Unit

The temperature sensor 5 measures the temperature of an object that issubject to temperature control, and transmits the temperature to thetemperature input unit 4. The temperature input unit 4 outputstemperature data indicating the temperature to the controller 2.

In the examples in FIGS. 1 and 2, the determination unit 34 isconfigured to determine whether or not one apparatus, namely the heater7 is disconnected. However, in the output control system 100 accordingto the invention, a configuration may also be adopted in which thedetermination unit 34 determines whether or not each of a plurality ofapparatuses are disconnected, and the warning output unit 35 may output,to the controller 2, a warning that makes it possible to distinguishwhich apparatus is disconnected.

To be more specific, for example, assuming that the output controlsystem 100 has a plurality of electric circuits that are eachconstituted by an SSR 8, a CT 9, and a heater 7 (and a heater powersupply) as shown in FIG. 2, the SSR control unit 32 gives driving orstopping instructions individually to the plurality of SSRs. The currentvalue acquisition unit 33 then acquires the individual values of thecurrents flowing in the heaters that are switched between driving andstopping by the SSRs, from CTs that are respectively connected to theheaters, and the determination unit 34 performs disconnectiondetermination for each of the heaters. The warning output unit 35 thenoutputs different warnings for the different heaters. This makes itpossible to individually detect disconnection of a plurality of heaters,and give warnings.

Method for Determining Heater Disconnection

Next, the determination that is performed by the determination unit 34will be described more specifically with reference to FIGS. 3A and 3B.FIG. 3A is a timing chart showing the temporal change of input/outputparameters in the temperature control unit 3.

The graph “instruction output” indicates timings of instruction outputfrom the SSR control unit 32 to the SSR 8 and the change of theinstruction. “ON” represents an instruction to drive the heater 7, and“OFF” represents an instruction to stop the heater 7. The graph “CTcurrent value” indicates the change in a current value that is acquiredby the current value acquisition unit 33 from the CT 9. Here, “currentvalue during shutoff” refers to a current value when the heater 7 isbeing stopped. On the other hand, “current value during conduction”refers to a current value when the heater 7 is being driven. Inaddition, as described above, the “disconnection determinationthreshold” is a value that is lower than the lower limit value of acurrent value when the heater 7 is being driven, and is determined asappropriate.

The graph “warning (monitoring information)” and the graph “warning(minor fault)” each show a timing when the warning output unit 35outputs a warning. The graph “warning (monitoring information)”indicates a case where a monitoring information warning is output, andthe graph “warning (minor fault)” indicates a case where a minor faultwarning is output.

The graph “event cancellation” indicates a timing when the acquisitionunit 30 acquires a warning event cancellation instruction from thecontroller 2 if the warning output unit 35 outputs a minor faultwarning. Note that, if a monitoring information warning is output, acancellation instruction as shown in this graph is not acquired.

As described above, the SSR control unit 32 transmits a drivinginstruction and a stop instruction to the SSR 8 through TPO. In otherwords, a pair of a period during which output of a driving instructioncontinues and a period during which output of a stop instructioncontinues is one control cycle. Here, if, as indicated by the firstcontrol cycle in FIG. 3A, a current value (i.e., a current valuemeasured by the CT 9) acquired by the current value acquisition unit 33is smaller than the disconnection determination threshold when the SSRcontrol unit 32 is outputting a driving instruction, the determinationunit 34 determines that the heater 7 is disconnected, and the warningoutput unit 35 outputs a monitoring information warning or a minor faultwarning to the controller 2, based on this determination. In addition,if a minor fault warning is output to the controller 2, the control unit20 of the controller 2 acquires the above warning, and outputs a warningevent cancellation instruction to the acquisition unit 30 of thetemperature control unit 3 if a predetermined condition is satisfied(e.g., if any measures have been taken to address the warning). Uponreceiving the cancellation instruction, the acquisition unit 30transmits this instruction to the warning output unit 35. Upon receivingthe event cancellation instruction, the warning output unit 35 stopsoutputting the minor fault warning.

Note that, if the current value received from the current valueacquisition unit 33 is continuously smaller than the disconnectiondetermination threshold for a predetermined number of times, thedetermination unit 34 may determine that the heater 7 is disconnected.FIG. 3B shows “CT current value” and the “warning” graphs (bothmonitoring information and minor fault warning) in more detail. One dotof the graph “CT current value” represents a timing when the CT 9samples a current value. In addition, the solid lines in the “warning”graphs indicate output timings of the monitoring information warning,and the broken lines indicate output timings of the minor fault warning.

As shown in FIG. 3B, if, after determining that the heater 7 isdisconnected, a current value received from the current valueacquisition unit 33 reaches a value larger than or equal to thedisconnection determination threshold+a predetermined buffer value (adisconnection determination hysteresis value in FIG. 3B) a predeterminednumber of times, the determination unit 34 may determine that the heater7 is not disconnected. In this manner, by determining whether or not theheater 7 is disconnected, based on a predetermined number of currentvalues, the determination unit 34 can reduce erroneous determinations.

Flow of Warning Output Processing

Lastly, in this embodiment, the flow of processing of the temperaturecontrol unit 3 outputting a warning (warning output processing) will bedescribed with reference to FIG. 4. FIG. 4 is a flowchart showing theflow of warning output processing.

When information regarding temperature adjustment is acquired from thecontroller 2, the acquisition unit 30 of the temperature control unit 3transmits the information to the SSR control unit 32. The SSR controlunit 32 generates an instruction to drive or stop the heater 7 accordingto the information, and transmits the instruction to the SSR 8 (stepS10) and the determination unit 34. On the other hand, at the timingwhen the SSR control unit 32 transmits the instruction to the SSR 8, thecurrent value acquisition unit 33 acquires a current value from the CT 9(step S11). The current value acquisition unit 33 transmits the acquiredcurrent value to the determination unit 34.

If an instruction for the SSR control unit 32 to drive the heater 7 hasbeen transmitted (YES in step S12), and the current value received fromthe current value acquisition unit 33 is smaller than or equal to thedisconnection determination threshold (YES in step S13), thedetermination unit 34 determines that the heater 7 is disconnected (stepS14). The determination unit 34 transmits the determination result tothe warning output unit 35. The warning output unit 35 generates awarning based on the determination result received from thedetermination unit 34, and outputs the warning (step S15).

On the other hand, if the SSR control unit 32 has transmitted aninstruction to stop the heater 7 (NO in step S12), or the current valuereceived from the current value acquisition unit 33 is larger than thedisconnection determination threshold (NO in step S13), thedetermination unit 34 determines that the heater 7 is being properlycontrolled, and then waits until it receives an instruction and acurrent value from the SSR control unit 32 and the current valueacquisition unit 33, respectively.

According to the above-described processing, the temperature controlunit 3 can determine whether or not the heater 7 is being driven orstopped according to an instruction to the SSR 8, based on the contentof the instruction to the SSR 8, namely, whether it is an instruction todrive the heater 7 or an instruction to stop the heater 7, and the valueof the current that flows in the heater 7. If the heater 7 is notproperly driven or stopped, it is possible to output a warning to thecontroller 2, which performs output control upstream of the temperaturecontrol unit 3.

In addition, according to the above-described processing, compared withthe case where the SSR 8 monitors and determines whether or not theheater 7 is being properly driven or stopped, it is possible to reducethe cost for introducing the SSR 8. In addition, it is not required towire the SSR 8 and the CT 9, and thus it is possible to reduce theman-hours for wiring. Furthermore, it is possible to save the troublefor various settings in the SSR 8 regarding monitoring of the heater 7.Therefore, the temperature control unit 3 can find an abnormality in theheater 7 with a simpler configuration, and warn the controller 2.

Note that, in this embodiment, if a current value acquired by thecurrent value acquisition unit 33 is larger than or equal to apredetermined threshold (second threshold) at the timing when the SSRcontrol unit 32 is outputting an instruction to stop the heater 7, tothe SSR 8, the determination unit 34 may determine that the heater 7 isnot being properly controlled due to a problem such as break-down of theSSR 8. A configuration may also be adopted in which the determinationunit 34 then informs the warning output unit 35 of the determinationresult, and the warning output unit 35 outputs a warning to thecontroller 2.

Furthermore, the warning output unit 35 may output different warnings(warnings that can be distinguished by the controller 2) for a casewhere the determination unit 34 determines that “the heater 7 isdisconnected” and a case where the determination unit 34 determines that“the SSR 8 is broken down”.

In addition, in this embodiment, the temperature control unit 3 may beconnected to an output apparatus for notifying the user of a warning.The output apparatus may be a speaker, a microphone, or the like. Thewarning output unit 35 of the temperature control unit 3 may also outputa warning via the connected output apparatus instead of outputting awarning to the controller 2, or in addition to outputting a warning tothe controller 2.

Accordingly, the temperature control unit 3 can cause the outputapparatus to output a warning generated by the temperature control unit3 without an instruction of the controller 2. Even if one of the devicesupstream of the temperature control unit 3, for example, the controller2 or the programmable display device 1 breaks down, and a warning is notsuccessfully transmitted to the upstream device, it is possible tonotify the user of the warning.

Second Embodiment

A configuration may also be adopted in which the temperature controlunit 3 according to the invention acquires, from the controller 2, anoperation amount indicating the ratio of a time during which an outputapparatus is driven per unit of time, and performs time proportionaloutput (TPO) of an instruction to drive or stop the heater 7 to the SSR8 such that a constant cycle and the time ratio indicated by theoperation amount can be realized. A second embodiment of the inventionwill be described below with reference to FIG. 5. Note that from thisembodiment onward, for convenience of description, the same referencenumerals are assigned to members having the same functions as themembers described in the first embodiment, and their further descriptionis omitted.

In this embodiment, a control unit 20 of a controller 2 outputs anoperation amount to a temperature control unit 3 via a secondcommunication unit 23. Specifically, the second communication unit 23adds the value of an operation amount to a data block, and returns thedata block to the communication network. Here, “operation amount” refersto a value designating the ratio of a time during which the heater 7 isdriven when the SSR 8 drives the heater 7. In the following description,as an example, the control unit 20 determines, as an operation amount, avalue that indicates the ratio of a time during which the heater 7 isdriven, and is expressed as a percentage (%), and outputs the value.

An acquisition unit 30 of the temperature control unit 3 acquires theabove-described operation amount, and transmits the operation amount toan SSR control unit 32. The SSR control unit 32 performs timeproportional output (TPO), to the SSR 8, in which a driving instructionand a stop instruction are combined, such that the time ratio indicatedby the above-described operation amount can be realized.

FIG. 5 is a timing chart showing the change in an operation amount thatis acquired by the acquisition unit 30 (instructed by the control unit20 of the controller 2) and the change in instruction output of the SSRcontrol unit 32. As illustrated, the graph “operation amount” indicatesthe value (%) of the operation amount acquired by the acquisition unit30. In addition, the graph “TPO output” indicates the content of aninstruction (ON or OFF of the heater 7) that is transmitted (output) bythe SSR control unit 32 to the SSR 8 through TPO and the period of TPO.In addition, points a to c indicate timings when the operation amountchanges, and arrows A to C indicate timings when changes in operationamount at the corresponding points a to c are reflected.

As illustrated, when an operation amount that is acquired by theacquisition unit 30 changes, the SSR control unit 32 reflects thechanged operation amount in the current TPO control cycle or the nextcontrol cycle.

More specifically, if the operation amount changes at the timing whenthe SSR control unit 32 is outputting a stop instruction (point a inFIG. 5), it suffices for the SSR control unit 32 to perform TPO during adriving time that is based on the changed operation amount, from thenext control cycle (arrow A in FIG. 5). In addition, if the operationamount changes at the timing when the SSR control unit 32 is outputtinga driving instruction (point b in FIG. 5), it suffices for the SSRcontrol unit 32 to adjust the period during which a driving instructionis output, and perform TPO such that the ratio of the driving time ofthe heater 7 in the current control cycle matches the time ratioindicated by the changed operation amount (arrow B in FIG. 5).

In addition, if the operation amount changes at the timing when the SSRcontrol unit 32 is outputting a driving instruction, and, in the controlcycle at this time, a driving time larger than or equal to a drivingtime indicated by the changed operation amount has already elapsed(point c in FIG. 5), it suffices for the SSR control unit 32 to outputan immediate stop instruction, and continue outputting a stopinstruction during the remaining time of the control cycle (arrow C inFIG. 5). In this case, the changed operation amount will be accuratelyreflected from the next control cycle (arrow C′ in FIG. 5).

Thus, even if an operation amount is determined without taking the cycletime of the control unit 20 and the TPO control cycle intoconsideration, there is the effect, that the operation amount can beappropriately reflected in TPO by the temperature control unit 3acquiring the value of the operation amount from the controller 2, andthe SSR control unit 32 performing TPO, as described above.

Third Embodiment

In addition, the temperature control unit 3 according to the inventionmay also acquire, from the controller 2, first information regardingdriving and stopping of the heater 7 and second information indicatingwhether or not to autonomously control TPO to the SSR 8. In addition,the temperature control unit 3 may also output an instruction to driveor stop the heater 7 to the SSR 8 through TPO in accordance with thefirst information and second information.

Here, for example, the first information may be the operation amountdescribed in the above embodiments, or may be a control instruction toturn on (drive) the heater 7, or to turn off (stop) the heater 7. Notethat the second information will be described in this embodiment.

The third embodiment of the invention will be described below withreference to FIG. 6. A controller 2 according to this embodiment isdifferent from the controller 2 according to the first and secondembodiments in that an operation amount (first information) andinformation (second information) indicating whether an immediate outputinstruction is ON or OFF are transmitted to a temperature control unit3. Also, the temperature control unit 3 is different from thetemperature control unit 3 according to the first and second embodimentsin that a method for controlling TPO to an SSR 8 is changed inaccordance with the above-described operation amount and whether theabove-described immediate output instruction is ON or OFF.

Here, “immediate output instruction” is information that takes twovalues, namely ON and OFF, and is information indicating whether or notto cause the temperature control unit 3 to autonomously control TPO tothe SSR 8. In the following description, if the immediate outputinstruction is ON, the temperature control unit 3 does not autonomouslycontrol TPO, and if the immediate output instruction is OFF, thetemperature control unit 3 autonomously controls TPO.

Here, “autonomously controlling TPO” refers to the temperature controlunit 3 determining start and end timings of TPO to the SSR 8 as well asa TPO control cycle based on the internal information of the temperaturecontrol unit 3 itself, for example. If the immediate output instructionis ON, the temperature control unit 3 cyclically acquires, via datablocks, instructions to start and end TPO or information indicating thestart and end timings that have been output from the controller 2. Thetemperature control unit 3 then changes start and end of TPO and the TPOcontrol cycle in accordance with these instructions or information.

Conversely, “not autonomously controlling TPO” refers to the temperaturecontrol unit 3 determining at least one of start and end timings of TPOto the SSR 8 and the TPO control cycle based on information (e.g., acontrol instruction or various parameters) that is acquired from thecontroller 2, for example.

In addition, the control unit 20 may also have an auto-tuning functionfor auto-tuning the heater 7. “Auto-tuning function” as mentioned inthis embodiment refers to a function for calculating various parametersrelated to output control such as PID control that is executed by thecontroller 2.

Furthermore, a configuration may also be adopted in which, in the caseof executing auto-tuning, the controller 2 stores, in a data block, thevalue ON as the value of the immediate output instruction, and outputsthis block. In addition, a configuration may also be adopted in which,in the case of not executing auto-tuning, the controller 2 stores, in adata block, the value OFF as the value of the immediate outputinstruction, and outputs this block. Below, it is assumed that, in thecase of executing auto-tuning, the controller 2 stores, in a data block,the value ON as the value of the immediate output instruction, and inthe case of not executing auto-tuning, stores, in a data block, thevalue OFF as the value of the immediate output instruction.

In addition, if the value of an immediate output instruction read outfrom a data block is ON, and an operation amount has changed, thetemperature control unit 3 may also update the TPO control cycle fromthe temperature control unit 3 to the SSR 8.

FIG. 6 is a timing chart showing changes in an operation amount and animmediate output instruction (second information) that are output fromthe control unit 20 of the controller 2, and TPO in an SSR control unit32 of the temperature control unit 3 and its control cycle.

When the immediate output instruction that is output from the controller2 is ON (i.e., when the control unit 20 of the controller 2 is executingauto-tuning), if an operation amount that is output from the controller2 along with the immediate output instruction changes, the SSR controlunit 32 updates the control cycle and starts one new control cycle evenif the current TPO has not been performed for a complete period (in FIG.6, a complete period corresponds to two seconds (s)) of one controlcycle (points f, g, h, and i in FIG. 6).

Note that, if a timing when the immediate output instruction changes toON and a timing when the operation amount changes are the same (point eFIG. 6), the SSR control unit 32 may update the control cycle asdescribed above, or may reflect the changed operation amount at thetiming when the next control cycle begins, without updating the controlcycle (an arrow E in FIG. 6).

In addition, if the timing when the immediate output instruction changesto OFF and the timing when the operation amount changes are the same(point j in FIG. 6), the SSR control unit 32 may also update the controlcycle as described above, or may also reflect the changed operationamount at the timing when the next control cycle begins, withoutupdating the control cycle (arrow J in FIG. 6).

As described above, if the operation amount changes while auto-tuning isbeing executed, the temperature control unit 3 can ensure thatauto-tuning is more accurately performed (more accurately calculatevarious parameters) on the controller 2, by reflecting the changewithout waiting for the next control cycle.

Particularly when the period of one control cycle is long, andreflection of a change in the operation amount is carried over to thenext control cycle, there are cases where there are deviations in thecalculation of the above-mentioned parameters. More specifically, forexample, in the case of a cooling device such as a fan, instead of theheater 7, one control cycle is often long, for example, 20 s. In thiscase, if a change of the operation amount is reflected in the nextcontrol cycle, the controller 2 will perform auto-tuning that is basedon the operation amount before the change, for a period of up to 20 s,and various parameters that are calculated may vary.

By contrast, if the control unit 20 of the controller 2 is executingauto-tuning, and the operation amount that is output by the controller 2changes, then the temperature control unit 3 according to thisembodiment updates the TPO control cycle, and resumes TPO based on thechanged operation amount. In other words, it can be said that thechanged operation amount is immediately reflected. Accordingly, thetemperature control unit 3 has the effect that it is able to cause thecontroller 2 to more accurately execute auto-tuning.

In addition, when the operation amount changes from 1% or more to 0%,the SSR control unit 32 of the temperature control unit 3 may alsoinstruct the SSR 8 to stop the heater 7 at the timing when the operationamount changes, regardless of the TPO control cycle. Furthermore, whenthe operation amount changes from 1% or more to 0%, the SSR control unit32 may also instruct the SSR 8 to stop the heater 7 at the timing whenthe operation amount changes, regardless of whether the immediate outputinstruction is ON or OFF.

Accordingly, when the heater 7 is to be stopped, the SSR control unit 32can transmit, to the SSR 8, an instruction to immediately stop theheater 7 regardless of the cycle of TPO. Therefore, the temperaturecontrol unit 3 can more quickly reflect the operation amount receivedfrom the controller 2.

In addition, if a plurality of SSRs 8 are connected to the temperaturecontrol unit 3, it is desirable that the controller 2 controls at leastone of start and end of TPO between the temperature control unit 3 andeach of the SSRs 8 and the TPO control cycle, in a distinguished manner(i.e. individually).

In addition, if the temperature control unit 3 is performing TPO to eachof a plurality of SSRs 8, and the controller 2 is to output (or isoutputting) the value ON as an immediate output instruction, thecontroller 2 may further transmit, to the temperature control unit 3,information indicating a start timing of TPO to each of the SSRs 8. Itis desirable that the acquisition unit 30 of the temperature controlunit 3 then acquires the above-described information indicating thetiming, and starts TPO of each of the SSRs 8 at the timing indicated bythe information indicating the start timing.

More specifically, a configuration may also be adopted in which thecontroller 2 adds, in a data block, a value (delay value) indicating thetime by which a start timing of TPO to each of the SSRs 8 is to bedelayed from the original start timing of TPO, as the above-describedinformation indicating the start timing, and outputs the data block. Aconfiguration may also be adopted in which the temperature control unit3 then reads the delay value, and delays the start timing of each TPO bythe time indicated by the delay value.

For example, assume that one temperature control unit 3 is connected toa plurality of SSRs 8, and the SSRs 8 are each connected to one or moreheaters 7. In this case, if TPOs to all of the SSRs 8 are turned ON atthe same time, there was a risk that an excessive current flows in thetemperature control unit 3, causing a malfunction.

By contrast, in the controller 2 and the temperature control unit 3according to this embodiment, for example, by the controller 2instructing different start timings of TPO between the temperaturecontrol unit 3 and the respective SSRs 8 (e.g., different delay valuesof TPO to the SSRs 8), it is possible to prevent an excessive electriccurrent from flowing as described above.

Modified Example

In the above embodiments, a system for adjusting the temperature of acertain target object by controlling driving of the heater 7 has beendescribed. However, the output control system 100 according to theinvention can be applied to not only temperature adjustment but alsovarious types of output control.

For example, a configuration may also be adopted in which the outputcontrol system 100 according to the invention has a burner in place ofthe heater 7, and performs temperature adjustment of a target object(e.g., water or metal) by controlling driving (ON) and stopping (OFF) ofthe burner. In this case, the SSR 8 (and the CT 9) may also be a controlmotor that has a function similar to that of the SSR 8 (and the CT 9).

In addition, a configuration may also be adopted in which the outputcontrol system 100 according to the invention has a tank filled with acoolant (e.g., water) in place of the heater 7, and performs temperatureadjustment of a target object by adjusting the area of the coolant thatcomes into contact with the target object, or adjusting the flow rate ofthe coolant. In this case, the SSR 8 (and the CT 9) may also be a valvemechanism for adjusting the area of the coolant that comes into contactwith the target object, the flow rate, and the like, the valve mechanismincluding a control function similar to that of the SSR 8 (and the CT9).

In addition, a configuration may also be adopted in which the outputcontrol system 100 according to the invention has a fan in place of theheater 7, and performs temperature adjustment of a target object bycontrolling driving and stopping of the fan. In this case, the SSR 8(and the CT 9) may also be a mechanism that has a control functionsimilar to that of the SSR 8 (and the CT 9), and controls driving,stopping, the rotation frequency, and the like of the fan.

In addition, a configuration may also be adopted in which the outputcontrol system 100 according to the invention has a Peltier element inplace of the heater 7, and performs temperature adjustment of a targetobject by controlling the Peltier element. In this case, the SSR 8 (andthe CT 9) may also be a Peltier controller that has a control functionsimilar to that of the SSR 8 (and the CT 9).

Realization Example Using Software

The controller 2 and control blocks of the temperature control unit 3(in particular, the control unit 20, the acquisition unit 30, the SSRcontrol unit 32, the current value acquisition unit 33, thedetermination unit 34, and the warning output unit 35) may also berealized by logic circuits (hardware) formed on an integrated circuit(IC chip), or may also be realized by software using a CPU (centralprocessing unit).

In the case of the latter, the controller 2 and the temperature controlunit 3 have a CPU that executes an instruction of a program that issoftware for realizing each function, a ROM (read only memory) or astorage apparatus (these are referred to as “recording media”) thatstores the program and various types of data in a computer-readable (orCPU-readable) manner, a RAM (random access memory) to which the programis loaded, and the like. An advantage of some aspects of the inventionis then achieved by a computer (or a CPU) reading the above-describedprogram from the above-described recording medium, and executing theprogram. A “non-transitory tangible medium” such as a tape, a disk, acard, a semiconductor memory, and a programmable logic circuit can beused as the above-described recording medium. In addition, theabove-described program may also be supplied to the above-describedcomputer via any transmission medium (e.g., a communication network orbroadcast wave) that can transmit the program. Note that the inventioncan also be realized in form of data signals that are obtained byembodying the above-described program through electric transmission, andare embedded in carrier waves.

An output control unit according to one aspect of the invention includesan acquisition unit that acquires, from a control apparatus, anoperation amount for a switching apparatus that switches between drivingand stopping of an output apparatus and an instruction output unit thatperforms time proportional output to the switching apparatus based onthe operation amount acquired by the acquisition unit.

A control method of an output control unit according to one aspect ofthe invention includes an acquisition step of acquiring, from a controlapparatus, an operation amount for a switching apparatus that switchesbetween driving and stopping of an output apparatus and an instructionoutput step of performing time proportional output to the switchingapparatus based on the operation amount acquired in the acquisitionstep.

According to the above-described configuration and processing, theoutput control unit itself that has acquired the operation amount fromthe control apparatus performs time proportional output to switchingapparatus. Here, “operation amount” refers to the ratio of a time duringwhich the output apparatus is driven. Therefore, for example, comparedwith a case where an instruction of time proportional output generatedby the control apparatus is acquired, and is transmitted to theswitching apparatus, the output control unit can perform timeproportional output independently of the cycle time of the controlapparatus.

Therefore, it is possible to avoid deviation of time proportional outputdue to the cycle time of the control apparatus. In addition, it is alsopossible to determine an operation amount without taking the cycle timeof the control apparatus into consideration, and perform timeproportional output.

In addition, in the output control unit, the acquisition unit may alsoperiodically acquire the operation amount from the control apparatus.Accordingly, it is possible to perform time proportional output withoutbeing affected by the acquisition cycle of the operation amount, andthus more accurate output control is possible.

In addition, in the output control unit, the acquisition unit may alsobe connected to the control apparatus via a field network. In the caseof performing communication using a field network, there are cases wherecommunication is cyclically performed. However, according to thisconfiguration, it is possible to perform time proportional outputwithout being affected by the communication cycle, and thus moreaccurate output control is possible.

In addition, in the output control unit, the instruction output unit mayperform time proportional output of an instruction, to the switchingapparatus, that instructs the switching apparatus to drive or stop theoutput apparatus, and if the operation amount that is acquired by theacquisition unit changes during one cycle of the time proportionaloutput and at a timing when an instruction to stop the output apparatusis being output to the switching apparatus, the instruction output unitmay perform the time proportional output based on the changed operationamount, starting with the next cycle following the one cycle.Accordingly, it is possible to reflect the change of the operationamount at a constant cycle without changing the period of one cycle oftime proportional output.

In addition, in the output control unit, the instruction output unit mayperform time proportional output of an instruction, to the switchingapparatus, that instructs the switching apparatus to drive or stop theoutput apparatus, and if the operation amount that is acquired by theacquisition unit changes during one cycle of the time proportionaloutput and at a timing when an instruction to drive the output apparatusis being output to the switching apparatus, the instruction output unitmay perform the time proportional output based on the changed operationamount, during the one cycle. Accordingly, it is possible to reflect thechange of the operation amount at a constant cycle without changing theperiod of one cycle of time proportional output.

In addition, in the output control unit, if the operation amount that isacquired by the acquisition unit changes at said timing, and theswitching apparatus has driven the output apparatus for at least aperiod indicated by the changed operation amount in the one cycle, theinstruction output unit may continue outputting an instruction to stopthe output apparatus to the switching apparatus for the remaining timeof the one cycle. Accordingly, it is possible to reflect the change ofthe operation amount at a constant cycle without changing the period ofone cycle of time proportional output.

An output control system according to one aspect of the inventionincludes the output control unit and the control apparatus. Accordingly,it is possible to realize an output control system that can preventdeviation of time proportional output due to the cycle time of thecontrol apparatus.

The invention is not limited to the above embodiments, and variousmodifications can be made within the scope of claims, and an embodimentacquired by appropriately combining technical means disclosed indifferent embodiments is also included in the technical scope of theinvention.

LIST OF REFERENCE NUMERALS

-   1 Programmable display device-   2 Controller (control apparatus)-   20 Control unit-   21 First communication unit-   22 Storage unit-   23 Second communication unit-   3 Temperature control unit-   30 Acquisition unit-   32 SSR control unit (instruction output unit)-   33 Current value acquisition unit-   34 Determination unit-   35 Warning output unit-   4 Temperature input unit-   5 Temperature sensor-   7 Heater (output apparatus)-   8 SSR (switching apparatus)-   9 CT

The invention claimed is:
 1. An output control unit comprising aprocessor configured with a program to perform operations comprising:operation as an acquisition unit that is connected to a controlapparatus different from the output control unit, via a field network,the acquisition unit configured to acquire, from the control apparatusthat operates at a specific cycle time, an operation amount for aswitching apparatus that switches between driving and stopping of anoutput apparatus; and operation as an instruction output unit configuredto perform time proportional output of an instruction to the switchingapparatus based on the operation amount acquired by the acquisitionunit, the instruction instructing the switching apparatus to drive orstop the output apparatus, wherein the operation amount comprises avalue that designates a ratio of a time during which the outputapparatus is driven and a time during which the output apparatus isstopped, the operation amount is determined according to the specificcycle time of the control apparatus, the output control unit changes acontrol cycle of the time proportional output based on an instructionfrom the control apparatus or on internal information of the outputcontrol unit itself, the specific cycle time of the control apparatusdiffers from the control cycle time of the time proportional outputperformed by the output control unit, and the processor is configuredwith the program to perform operation such that operation as theinstruction output unit comprises performing time proportional output ofthe instruction to the switching apparatus, that instructs the switchingapparatus to drive or stop the output apparatus, and if the operationamount that is acquired by the acquisition unit changes during one cycleof the time proportional output and at a timing when the instruction todrive the output apparatus is being output to the switching apparatus,adjusting a period during which the instruction to drive the outputapparatus is output, and performing the time proportional output suchthat the ratio of the driven time and stopped time of the timeproportional output in the one cycle matches the ratio of the timeduring which the output apparatus is driven and the time during whichthe output apparatus is stopped indicated by the changed operationamount.
 2. The output control unit according to claim 1, wherein theprocessor is configured with the program to perform operation such thatoperation as the acquisition unit comprises periodically acquiring theoperation amount from the control apparatus.
 3. The output control unitaccording to claim 1, wherein the processor is configured with theprogram to perform operation such that operation as the instructionoutput unit comprises performing time proportional output of aninstruction, to the switching apparatus, that instructs the switchingapparatus to drive or stop the output apparatus, and if the operationamount that is acquired by the acquisition unit changes during one cycleof the time proportional output and at a timing when an instruction tostop the output apparatus is being output to the switching apparatus,performing the time proportional output based on the changed operationamount, starting with the next cycle following the one cycle.
 4. Theoutput control unit according to claim 1, wherein the processor isconfigured with the program to perform operation such that operation asthe instruction output unit comprises, if the operation amount that isacquired by the acquisition unit changes at the timing when theinstruction to drive the output apparatus is being output to theswitching apparatus, and the switching apparatus has driven the outputapparatus for at least a period indicated by the changed operationamount in the one cycle, outputting an instruction to stop the outputapparatus to the switching apparatus for the remaining time of the onecycle.
 5. An output control system comprising: the output control unitaccording to claim 1; and the control apparatus, wherein the controlapparatus is configured to operate at a specific cycle time.
 6. Acontrol method of an output control unit, comprising: acquiring, from acontrol apparatus different from the output control unit and connectedto the output control unit via a field network, an operation amount fora switching apparatus that switches between driving and stopping of anoutput apparatus, the control apparatus operating at a specific cycletime; and performing time proportional output of an instruction to theswitching apparatus based on the acquired operation amount, theinstruction instructing the switching apparatus to drive or stop theoutput apparatus, wherein the operation amount comprises a value thatdesignates a ratio of a time during which the output apparatus is drivenand a time during which the output apparatus is stopped, the operationamount is determined according to the cycle time of the controlapparatus, a control cycle of the time proportional output is changedbased on an instruction from the control apparatus or on internalinformation of the output control unit itself, the specific cycle timeof the control apparatus differs from the control cycle time of the timeproportional output, and the processor is configured with the program toperform operation such that operation as the instruction output unitcomprises performing time proportional output of the instruction to theswitching apparatus, that instructs the switching apparatus to drive orstop the output apparatus, and if the operation amount that is acquiredby the acquisition unit changes during one cycle of the timeproportional output and at a timing when the instruction to drive theoutput apparatus is being output to the switching apparatus, adjusting aperiod during which the instruction to drive the output apparatus isoutput, and performing the time proportional output such that the ratioof the driven time and stopped time of the time proportional output inthe one cycle matches the ratio of the time during which the outputapparatus is driven and the time during which the output apparatus isstopped indicated by the changed operation amount.
 7. The output controlunit according to claim 2, wherein the processor is configured with theprogram to perform operation such that operation as the instructionoutput unit comprises performing time proportional output of aninstruction, to the switching apparatus, that instructs the switchingapparatus to drive or stop the output apparatus, and if the operationamount that is acquired by the acquisition unit changes during one cycleof the time proportional output and at a timing when an instruction tostop the output apparatus is being output to the switching apparatus,performing the time proportional output based on the changed operationamount, starting with the next cycle following the one cycle.
 8. Theoutput control unit according to claim 2, wherein the processor isconfigured with the program to perform operation such that operation asthe instruction output unit comprises, if the operation amount that isacquired by the acquisition unit changes at said timing, and theswitching apparatus has driven the output apparatus for at least aperiod indicated by the changed operation amount in the one cycle,continuing outputting an instruction to stop the output apparatus to theswitching apparatus for the remaining time of the one cycle.
 9. Anoutput control system comprising: the output control unit according toclaim 2; and the control apparatus, wherein the control apparatus isconfigured to operate at a specific cycle time.
 10. The output controlunit according to claim 1, wherein the processor is configured with theprogram to perform operation such that operation as the instructionoutput unit comprises, if the operation amount that is acquired by theacquisition unit changes at said timing, and the switching apparatus hasdriven the output apparatus for at least a period indicated by thechanged operation amount in the one cycle, continuing outputting aninstruction to stop the output apparatus to the switching apparatus forthe remaining time of the one cycle.
 11. The output control unitaccording to claim 1, wherein the processor is configured with theprogram to perform operation such that operation as the instructionoutput unit comprises, if the operation amount that is acquired by theacquisition unit changes at the timing when the instruction to drive theoutput apparatus is being output to the switching apparatus, and thedriving time of the time proportional output is larger than or equal tothe driving time indicated by the changed operation amount has alreadyelapsed, outputting an instruction to stop the output to the switchingapparatus for the remaining time of the one cycle.